Power converters for renewable energy power conversion, motor drives and uninterruptible power systems (UPS) all use three basic power component types; semiconductor devices, magnetic components and capacitors. All power components generate waste heat in the power conversion process.
Semiconductor devices generate heat due to conduction, switching and diode recovery losses. The waste heat must be transferred out of the device to limit the semiconductor die temperatures to safe maximums. Semiconductors are typically the primary source of power converter waste heat.
Magnetic components such as transformers and filter inductors have copper and core losses that generate heat, heat which must be removed to maintain the core properties and to protect the integrity of the electrical insulating materials.
Power capacitors used across a DC buss or as AC filters also generate heat from ripple currents acting against the internal impedance of a capacitor. Although the overall load on a power converter cooling system from capacitors is small compared to semiconductor and magnetic component losses, capacitors must operate at much lower temperatures to ensure their longevity.
The power rating of any power converter is a function of the power device ratings and the efficiency of the heat removal process. The usable lifetime of any power converter is directly related to the operating temperature of its component parts. These factors directly impact the cost, performance and reliability of any power converter.